Drill, especially rock drill

ABSTRACT

A drill, especially a masonry and rock drill, in which a fluted shank has a transverse slot in the working end and a hard cutting plate seated in the slot and retained therein by a pin removably mounted in the shank. The cutting plate may be indexable in the slot to expose respective regions thereof for cutting operations. The cutting plate engages the bottom of the slot and is supported thereby. The engagement of the cutting plate by the bottom and side walls of the slot and by the pin holds the cutting plate against displacement in the slot.

Umted States Patent 1191 1111 3,878,905

Schaumann Apr. 22, 1975 DRILL, ESPECIALLY ROCK DRILL 2.575.239 11/1951Stephens 175/383 2,888,247 5/1959 H l d l75/410 X [75] Schwmam't wemgamm2.902.260 9/1959 T1155: 175/394 Germany 3,052,310 9/1962 Kinzbach175/410 3.089.552 5/1963 Black et al 175/410 X [73] Ass'gnee' g gz zz3.330.601 7/1967 Proctor .175/413 x 23 sverkzeugfabfic 3,672,455 6/1972Foster 175/418 x Ravensburgh Ravensburg Germany 715.145 9/1931 France175/394 22 F I I [led Apr 1973 Primary E.\'aminerErnest R. Purser [21]Appl. No.: 349,611 Assistant Examiner-Richard E. Favreau Attorney,Agent, or FirmWalter Becker [30] Foreign Application Priority Data Apr.7. 1972 Germany 2216760 I'7] ABSTRACT A drlll. especially a masonry androck drlll, 1n Wl'llCh a [52] CL 175/383; 175395. 75/415. fluted shankhas a transverse: slot in the working end 299/92 and a hard cuttingplate seated in the slot and retained 511 1m. 01. E2lc 13/08 herein by aPin mm/ably mounted in the shank- The 158 Field of Search 175/394, 395,410, 383, cutting Plate may be indexable in to expose 175mm 413 414 415,313; 299/92 respective regions thereof for cutting operations. The

cutting plate engages the bottom of the slot and is sup- [56] ReerencesCited ported thereby. The engagement of the cutting plate UNITED STATESPATENTS by the bottom and side walls of the slot and by the pin holdsthe cutting plate against displacement in the 395,034 12/1888 Coffin175/401 X slot. 994.668 6/1911 Childs 175/383 2.205.238 6/1940 Burt175/410 X 36 Claims, 13 Drawing Figures DRILL, ESPECIALLY ROCK DRILL Thepresent invention relates to a drill, especially rock drill, with adrill shank which has its circumferential surface provided with at leastone groove for the drilling dust and which has its drill head providedwith a transverse slot having inserted thereinto a plateshaped cuttingmember which is located in an axial plane of the drill shank and is madeof hard metal.

It is an object of the present invention so to design a drill of thementioned type that, when the drill becomes dull, it will be possible ina short time to provide the same with a new sharp blade or cutting edgewhile the design is such that the cutting member will be safely held inthe drill head.

This object and other objects and advantages of the invention willappear more clearly from the following specification in connection withthe accompanying drawings, in which:

FIG. 1 represents a view showing a cutout portion of a drill accordingto the invention.

FIG. 2 illustrates a section taken along the line II II of FIG. 1.

FIG. 3 is a section taken along the line III III of FIG. 2.

FIG. 4 shows a top view of the drill of FIG. 1.

FIG. 5 represents a further embodiment ofa drill according to theinvention and is illustrates similar to FIG. 4.

FIG. 6 is a view of still another embodiment of the cutting member in adrill according to the invention.

FIG. 7 shows the cutting member of FIG. 6 as seen in the direction ofthe arrow A of FIG. 6.

FIGS. 8-l0 show still another embodiment of a drill according to theinvention and illustrated in a manner corresponding to that of FIGS.1-3.

FIG. ll illustrates another embodiment of a drill according to theinvention in an illustration similar to that of FIG. 9.

FIG. 12 is a section taken along the line XII-XII of FIG. ll.

FIG. I3 shows a further embodiment of a drill according to the inventionin an illustrated corresponding to that of FIG. 3.

The drill according to the present invention which has its drill shankprovided with at least one groove for the drilling dust and has itsdrill head provided with a transverse slot in which is inserted aplate-shaped cutting member of hard metal or the like is characterizedprimarily in that the cutting member which is exchangeably inserted intothe transverse slot is by means of a detachable holding element securedrelative to the drill shank, the holding member being formed by a boltwhich is located about at a right angle with regard to the drill axisand is arranged within the enveloping surface of the drill. This boltengages recesses in the drill shank and in the cutting member.

In this way the cutting member may at any desired time quickly beexchanged while the arrangement of the bolt in conformity with theinvention will assure a safe holding of the cutting member.

According to a simple embodiment of the drill according to theinvention, the bolt is located at a right angle with regard to thecutting member while engaging the cutting member only over a shortportion of its length. When the bolt is arranged parallel to the planeof the cutting member, the bolt will be able for all practical purposesover the entire width of the cutting member to engage the cutting memberand the drill shank. It is furthermore expedient to have the boltlocated approximately symmetrically with regard to the cutting member.In order to realize particularly favorable strength conditions, the axisof the bolt intersects with the axis of the drill.

For further simplifying the construction of the drill, the bolt engagesa recess forming a passage, especially a bore, provided in the cuttingplate and/or the drill shank. However, it is also possible that the boltengages a groove, especially a groove of a cutting plate and/or of thedrill shank while the groove corresponds in cross section to the bolt sothat the cross section of the cutting blade or of the drill shank neednot be completely perforated for receiving the bolt. According to anembodiment which is simple to handle, the groove is provided on alateral surface of the cutting member and/or the cross sectional slot ofthe drill shank. The groove in the cutting plate may extend over theentire width of the cutting plate so that the bolt can easily beintroduced and pulled out again. For realizing a safe guiding of thebolt, at least one groove, especially the groove in the drill shank, isundercut. 'The groove in the cutting member and the groove in the drillshank form a passage bore for the bolt so that the latter will be safelyheld and a high strength connection will be assured between the cuttingmember and the drill shank.

In order to be sure that in spite of the relatively large cross sectionof the bolt also very thin cutting plates may be employed, the groove inthe cutting member has a flatter depth than the groove in the drillshank, especially a depth which is approximately one third of the depthof the groove in the drill shank.

A particularly advantageous design of the invention consists in that thebolt is offset relative to the central axis of the recess in the cuttingmember toward the bottom of the transverse slot so that the bolt whenbeing introduced will be preloaded in a direction transverse to thelongitudinal direction of the bolt in such a way that with this preloadit will press the cutting member against the bottom of the transverseslot and thus will assure a completely play-free hold of the cuttingmember. This may also be realized by forming one recess, especially therecess in the cutting member for the bolt, by an elastic spring memberinserted into a correspondingly larger receiving opening. The springmember is formed in a simple manner by a spring sleeve and preferablymay be of rubberelastic character.

It is furthermore possible as bolts to provide screw bolts. However, aparticularly simple construction and a very simple handling will beobtained when the bolt is formed by a press pin, in particular a spiralclamping pm.

For purposes of resting and avoiding relative movements between thecutting plate and the drill, the cutting member has that edge thereofwhich faces away from the cutting edge arranged in engagement with thebottom of the transverse slot, preferably approximately over the entirediameter of the drill shank.

A further increase in the strength of the drill can be realized byproviding the transverse slot and/or the bolt symmetrically with regardto the end sections of the drilling dust grooves which end sections areprovided on the drill head and in particular are approximatelyaxis-parallel with regard to the drill. In this way also a morefavorable drilling dust removal directly from the drill tip will beassured. This arrangement will be further improved when the end sectionsof the drilling dust grooves are located on both sides of the transverseslot and/or of the bolt at a distance from the bolt.

A very favorable removal of drilling dust at high drill strength,especially within the region of the drill tip, is obtained when the endsections of the drilling dust grooves merge in the direction toward thecenter of the drill shank and in axial spacing from the bottom of thetransverse slot with spiral drilling dust grooves. It is also within theframework of the present invention to have the drill at thecircumference thereof provided with merely one or two lateralaxis-parallel flat grooves or the like for the removal of the drillingdust. For increasing the cross section of the drill head, the width ofthe end sections is less than the width of the spiral-shaped drillingdust grooves. According to the invention, two or four drilling dustgrooves may be provided so that also a larger quantity of obtaineddrilling dust can quickly be withdrawn.

For realizing a high drilling output, the respective cutting edge of thepreferably multi-edged cutting member. which may have one or morecutting edges, is formed by two cutting edges forming an acute anglewith each other and located symmetrically with regard to the axis of thedrill. Expediently, each cutting edge located approximately in thecentral plane of the cutting member is formed by inclined areas of theedges of the cutting member. The cutting member has a support with avery large surface in the drill head when the edges are located towardthe center of the cutting member and pertaining to the inclined surfacesof the cutting plate are located at the edges of the transverse slot sothat only the inclined areas protrude. ln this way an optimum design canbe obtained by having the drill head provided with a conical end theconical angle of which is preferably greater than the cutting edge angleof the cutting member and/or equals the angle between the two cuttingedges of the cutting member.

For further improving the withdrawal of the drilling dust. the endsections of the drilling dust grooves extend into the conical end ofthedrill head while preferably its end edges are located directly adjacentto the edges of the transverse slot and approximately parallel thereto.With a particularly advantageous design of the drill according to theinvention, the conical end of the drill head is arranged in spacedrelationship to the bolt on that side thereof which faces toward thecutting edge so that the bolt may be held in the drill shank over theentire diameter thereof.

For obtaining a precise alignment of the cutting member with regard tothe drill shank, the bottom of the transverse slot has a centeringdepression for engagement by a protrusion of the cutting member. Thiscentering depression may be formed, for instance, by a V-shapedformation of the bottom of the transverse slot so that a prism-shapedcentering depression will be obtained. However, it is also possible thatthe preferably plane bottom of the transverse slot extends approximatelyat a right angle to the axis of the drill, while preferablyapproximately in the center of the length of the drill the bottom hasthe centering depression which may, for instance, be of rectangularcontour. A corresponding projection on the cutting member is associatedwith the centering depression.

A particularly advantageous further development of the inventionconsists in that the cutting member which is approximately centrallysymmetrical and designed as a reversible plate has at least twopreferably diametrically oppositely located cutting edges so that oneand the same cutting member, by being turned over, can be employed aplurality of times. If only two cutting edges are provided which arelocated opposite to each other. the edges of the reversible plate whichinterconnect the two cutting edges are shorter than the cutting edges sothat the depth of the transverse slot need only be relatively small.

It is also possible that all edges of the preferably hexagonalreversible plate are designed as cutting edges so that, for instance,three cutting blades with two cutting edges each are available.

With the drill according to the invention the bolt may be used merelyfor preventing the loss of the cutting part, whereas when working withthe drill the bolt has for all practical purposes not to absorb anyforces because the drilling forces occurring during the working with thedrill press the cutting part into the drill shank and, morespecifically, into the transverse slot. in order to assure that only thecutting plate is exposed to wear and that as little of the shaft of thedrill as possible is exposed to wear, the cutting part protrudeslaterally beyond the circumference of the drill head, preferably by lessthan the width of the inclined surfaces forming the cutting edges.

Referring now to the drawings in detail and, more specifically to FIGS.1-4, the drill illustrated therein comprises a drill shank l which isprovided with a helical groove 2 for the drilling dust. At its workingend, the drill has a drill head 3 in front of which the groove 2 ends insuch a way that the drill head has a relatively large cross section. Theend 4 of the drill head 3 is conical with an obtuse angle. In the drillhead 3, symmetrically with regard to an axial plane of the drill shank 1there is provided a transverse slot 5. The bottom 6 of slot 5 is, whenviewed at a right angle to the lateral surfaces 7 of the slot 5,symmetrical with regard to the axis of the drill and is V-shaped with anobtuse angle. The V-angle of bottom 6 substantially equals the conicalangle of the end 4 of the drill head 3. The bottom 6 of the transverseslot 5 is in cross section V-shaped with an acute angle. In the drillhead 3 at a right angle to the central plane of the transverse slot 5there is provided a passage bore 8 the central axis of which intersectsthe axis of the drill. The bore 8 is approximately in the middle betweenthe tips of the end 4 of the drill head 3 and of the bottom 6 of thetransverse slot 5 located in such a way that it is arranged outside theend 4 of the drill head 3 and, more specifically, in that sectionthereof which is substantially cylindrical. Diagonally or diametricallyon both sides of the transverse slot 5, two end sections 9, 10 of thegroove 2 are located opposite to each other. These end sections 9, 10are located symmetrically with regard to a common axial plane of thedrill shank l in such a way that one leg 11 each of its rectangularV-shaped cross section is parallel to the central plane of thetransverse slot 5 while the other leg 12 is located parallel to thecentral axis of bore 8. The legs 11 are directly adjacent to therespective pertaining edge 13 which is formed by the correspondinglateral surface 7 of the transverse slot 5 and the conical mantlesurface of the end 4 of the drill head 3, the legs .being parallel tothe edge 13. One groove end section 9 is angled off and merges with thatend of the helical groove 2 which is adjacent the drill head 3, whereasthe other groove section is located in spaced relationship to this endand merges with the helical groove 2.

Inserted into the transverse slot 5 of the drill head 3 is a centrallysymmetrical flat cutting plate 14 which has lateral surfaces 15 arrangedparallel to each other and substantially over its entire surface engagesthe lateral surfaces 7 of the transverse slot 5. The cutting plate 14which in view forms a regular hexagon has six cutting edges 16 whichform acute angles with each other and merge with each other. Thesecutting edges 16 are each formed by two flat portions 17 of the edges ofthe cutting plate 14, these edges being symmetrically arranged withregard to the central plane of the plate 14. The flattened portions 17form an acute angle with each other. Each two adjacent cutting edgesform the drill cutting edge 18 and the drill tip 19 which is located inthe axis of the drill. The cutting edges 16 which are parallel to eachother are spaced from each other by a distance slightly greater than thediameter of the drill head 3 or drill shank 1 and in such a way that twocutting edges 16 each are provided slightly beyond the circumference ofthe drill head 3 and are located in an axis-parallel manner with regardto the drill.

The V-shape of the bottom 6 of the transverse slot 5 as well as itsV-shaped cross section are so selected that with the cutting blade 14inserted, two cutting edges 16 as well as their pertaining flattenedportions 17 engage the bottom 6 substantially over their entire surfaceand thus form a centering protrusion 20 by means of which the cuttingplate is secured against accidental lateral displacement in thetransverse slot 5. With the inserted cutting plate, the inner edges 21of the flattened portions 17 forming the cutting blade 18 are locatedover their entire length at the edges 13 of the transverse slot 5,whereas the inner edges 21 of the flattened portions 17 of the cuttingedge 16 which is parallel to the axis of the drill are located withinthe lateral edges 22 of the transverse slot 5.

The cutting plate 14 has in its central axis a passage bore 23 thediameter of which is from 1.2 to 2.5 times greater than the diameter ofthe drill 8. In this bore 23 there is inserted an elastic rubber sleeve24, preferably under preload. The inner bore of the rubber sleeve 24 hasa diameter which substantially equals in size the bore 8 or is smallerthan the latter. The inner bore 25 is located coaxially with regard tothe outer circumference of the sleeve 24. When the cutting plate 14 isinserted, its bore 23 is by a predetermined eccentricity further removedfrom the bottom 6 of the transverse slot 5 than the bore 8 of the drillhead 3. The inserted cutting plate 14 is held by means ofa pin 26 whichhas its end pressed into the bore 8 of the drill head 3. Pin 26 ispassed through bore 25 of the rubber sleeve 24 in such a way that theinner bore 25 of the rubber sleeve 24 is coaxial with the bore 8 so thatthe rubber sleeve 24 is braced in this direction toward the bottom 6 ofthe transverse slot 5. In this way the cutting plate 14 is pressedelastically against the bottom 6 of the transverse slot 5. After the pin26 has been knocked out at least partially, the plate 14 can be removedfrom the transverse slot 5 and can then be turned about its axis and canagain be inserted and secured by the pin 26 so that other cutting edges16 of the cutting plate 14 will now form the cutting edge of the drill.The axial extension of the rubber sleeve 24 is in thespecific embodimentshown in the drawings equalling the thickness of the cutting plate 14while the rubber sleeve 24 may be adherently connected to the cuttingplate 14.

As will furthermore be seen from FIG. 4, when viewing in axial directiontoward the drill, the cutting plate 14 and the pin 26 are locatedrelative to each other at a right angle and in a cross-like manner whilethe groove end sections 9, 10 are provided in two diametricallyoppositely located corners of this cross in such a way that theirlateral surfaces are arranged in spaced relationship to the cuttingplate 14 and the pin 26. The diameter of pin 26 is only slightly lessthan the thickness of the cutting plate 14.

According to the embodiment illustrated in FIG. 5, in all four cornersof the cross passing through the cutting plate 14a and the pin 26a thereare provided groove end sections 9a, 10a in such a way that always twogroove end sections 90, 10a are located diametrically opposite to eachother and symmetrically to a common axial plane of the drill or drillhead. Accord ing to the embodiment of FIGS. 1-4 and, more specifically,however, with the embodiment of FIG. 5, instead of one groove for thedrilling dust also two helical drilling dust grooves may be provided.

The cutting plate 14b is, in conformity with FIGS. 6 and 7, providedwith only two cutting members 18b each having two cutting edges; 16barranged at an angle with regard to each other. These two cuttingmembers 18b are located opposite to each other and symmetrically withregard to a common axial plane of the cutting plate 14b. The lateraledges 27 of the cutting plate 14b which interconnect the cutting members18b are located parallel to each other and while being plane over theentire thickness of the cutting plate 14b are shorter than the cuttingedges 16b.

According to the embodiment illustrated in FIGS. 8-10, the cutting plate14c is provided with only one single cutting member 180. For this reasonthe cutting plate 14c is not designed as reversible plate. Thetransverse slot 5c provided in the drill head 30 of the drill shank It"has a bottom 60 which is substantially plane and extends at a rightangle with regard to the drill axis. The bottom 60 is provided at thecenter of its length with a rectangular, circular or oval centeringdepression 28 which extends over the entire width of the transverse slot5c. At that edge which faces away from the cutting member 180 whichlatter is formed by two cutting edges arranged at an angle with regardto each other, the cutting plate is provided with a centering protrusion20c which fits into the centering depression 28. The arrangement is suchthat the cutting plate 14c rests on both sides of the centeringprotrusion 20c with its corresponding edge on the bottom 60 of thetransverse slot 5c. Provided in the cutting plate 14c is a passage bore230 the diameter of which is approximately equal to the diameter of thepassage bore 8: in the drill head 3c in such a way that the pin 26c ispressed directly into the cutting plate 140. The distance between thepin 26c from the bottom 6c of the transverse slot 50 is with thisembodiment smaller than the distance of the pin 26c from the cuttingmember 18c or from the cutting tip 19c.

The embodiment according to FIGS. 11 and 12 differs from that of FIGS. 810 primarily in that the pin 26d which has the shape of a clamping pinis parallel to the plane of the cutting plate 14d while the cuttingplate 14d has one lateral surface 15d provided with a groove 23d and thetransverse slot 5d has the pertaining lateral surface 7d likewiseprovided with a groove 8d. The grooves 23d, 8d form with the insertedcutting plate 14d a bore-like passage for the bolt 26d. The depth ofgroove 9d is greater than half the diameter of the pin 26d to such anextentthat this groove can be designed as an undercut-groove and willalone suffice for guiding and holding the pin 26d pressed thereinto. Theradius of curvature of the cross section of groove 23d in the cuttingblade 14d is slightly greater than the radius of curvature of the crosssection of pin 26d, while the longitudinal central plane of groove 23dis furthermore slightly farther spaced from the bottom of the transverseslot d than is the longitudinal central plane of the groove 8d so thatthe pin 26:! substantially engages only that lateral surface of groove23d under preload which is located toward the bottom of the transverseslot 5d, whereby the cutting plate 1411 is pressed against the bottom ofthe transverse slot 5d.

As is furthermore evident from FIGS. 11 and 12, with this embodiment thedrill shank 1d, instead of being provided with drilling dust grooves,has two lateral axisparallel flattened portions 2d which are parallel tothe cutting plate 14d and which extend over the entire length of thedrill shank 1d up to the end of the drill head 3d.

As shown in FIG. 13, the bottom surface 28e provided for engagement withthe cutting plate l4e may also be formed by a separate insert member 29consisting of hard metal. The insert member 29 is arranged in the head3e of the drill 1e. The insert member 29 is likewise plate-shaped andhas a thickness which approximately equals the thickness of the cuttingplate 14e. The insert member 29 is arranged in the transverse slot inthe drill head 3e which thus is deeper by the height of the insertmember 29. The bottom surface 6e of this transverse slot, which over itsentire height has plane side walls, is in the shape of a pitch circlecurved concavely while the axis of curvature is spaced from the drillhead 3e and intersects at a right angle the axis of the drill head 3e sothat the bottom surface 6e can be manufactured in a simple manner by aside milling cutter. That surface of the insert member 29 which over itsentire surface engages the bottom surface 6e of the transverse slot iscurved correspondingly so that the drill head 3e and the insert member29 are centered relative to each other when the cutting plate Me isinserted. The insert member 29 may, however, also be connected in thetransverse slot by soldering, pressing. welding as well as by ultrasoundor electron beam weldmg.

In the center of the slot bottom provided for engagement with thecutting plate, there is furthermore provided a bore for manufacturingreasons. If, however, the member containing the transverse slot ispressed in later, the said bore will be superfluous. With the embodimentaccording to FIG. 13, it is possible better to absorb the high forcesoccurring in the bottom of the slot.

It is, of course, to be understood that the present invention is, by nomeans, limited to the particular showing in the drawings but alsocomprises any modifications within the scope of the appended claims.

What is claimed is:

I. In a drill for masonry and rock; a drill shank having a working end,longitudinally extending dust groove means formed in said shank andextending along the shank from said working end, a transverse slotformed in the working end of said shank, a cutting plate formed of hardwear resistant material seated in said slot, and a retaining pinextending through said shank substantially perpendicular to the axis ofsaid shank and also engaging said cutting plate and retaining said platein said slot. said pin being moveable in said shank in the axialdirection of said pin to release said cutting plate from said slot, saidcutting plate being polygonal when viewed in a direction perpendicularto the plane thereof, at least the axially outer end of the cuttingplate having a point on the axis of the drill shank and incliningrearwardly from the point in, both directions when viewed perpendicularto the plane of the cutting plate, the said outer end of the cuttingplate being bevelled on opposite sides to form cutting edges thereon,the working end of said shank being conical and tapering inwardly, therebeing a bottom and side edges of the open end of said slot meeting wherethe slot intersects the conical end of the shank being in about theplanes of the bevels on the outer end of said cutting plate, the angleon the working end of the drill shank being greater than the anglebetween the bevels on the outer end of said cutting plate, said groovemeans in said shank comprising a terminal portion at the working end ofsaid shank disposed immediately forward of the leading side of saidcutting plate at each lateral end thereof.

2. A drill according to claim 1 in which said pin is generally centrallylocated with respect to said cutting plate and is perpendicular to theplane of the cutting plate and extends through said cutting plate.

3. A drill according to claim I in which said pin is substantiallyparallel to the plane of said cutting plate.

4. A drill according to claim 1 in which the axis of said pin intersectsthe axis of said shank.

5. A drill according to claim 1 in which said pin is disposed along saidshank between the conical end thereof and the bottom of said slot.

6. A drill according to claim 1 in which said cutting plate issymmetrical about at least one central axis which is parallel to theplane of the cutting plate and perpendicular to the axis of the shankwhen the cutting plate is seated in said slot, each edge of the cuttingplate facing away from said central axis having a cutting edge formedthereon, the bottom of said slot being formed for supportingly engagingthe axially inner cutting edge while the axially outer cutting edge isin working position.

7. A drill according to claim 1 in which said slot is formed with acentering recess therein and said cutting plate has a protrusion thereonwhich engages said recess when the cutting plate is positioned in saidslot.

8. A drill according to claim 7 in which the bottom of said slot isperpendicular to the axis of said shank and said centering recess is inthe middle of the length of the bottom of said slot.

9. A drill according to claim 7 which includes a hard insert member insaid slot and forming the bottom thereof.

10. In a drill for masonry and rock; a drill shank having a working end,longitudinally extending dust groove means formed in said shank andextending along the shank from said working end, a transverse slotformed in the working end of said shank, a cutting plate formed of hardwear resistant material seated in saidslot, and a retaining pinextending through said shank substantially perpendicular to the axis ofsaid shank and also engaging said cutting plate and retaining said platein said slot, said pin being moveable in said shank in the axialdirection of said pin to release said cutting plate from said slot, thebottom of said slot being in the form of a segment of a cylinder havingan axis disposed outwardly from the working end of the shank andintersecting the axis of the shank at a right angle.

11. drill according to claim in which said shank has a drilled holetherein into which said pin closely fits.

12. A drill according to claim 10 in whichsaid shank has a transversehole therein parallel tov the plane of said slot and offset laterallyfrom the axis of said shank,

said pin closely fitting said hole and on one side extending into saidslot, said cutting plate having a groove formed in the side facing saidpin to receive said pin.

13. A drill according to claim .10 in which a groove is formed along oneside ofsaid slot perpendicular to the axis of said shank, said cuttingplate having a groove formed therein on the side facing the groove inthe shank and in registration'therewith, said grooves forming a space toreceive said pin.

14. A drill according to claim 10 in which said cutting plate ispolygonal when viewed in a direction perpendicularto the plane thereof,at least the axially outer end of the cutting plate having a point onthe axis of the drill shank and inclining rearwardly from the pointinboth directions when viewed perpendicular to the plane of thecuttingplate, the said outer end of the cutting plate being bevelled onopposite sides to form cutting edges thereon, the working end of saidshank being conical and tapering inwardly, the side edges of the openend of said slot meeting where the slot intersects the conical end ofthe shank being in about the planes of the bevels on the outer end ofsaid cutting plate.

15. A drill according to claim 10 in which said cutting plate whenviewed perpendicular to the plane thereof is a regular polygon, all ofthe edges of said cutting plate being bevelled to form a cutting edgeextending about'the entire periphery of said cutting plate, said I platebeing angularly indexable in said slot for successively presentingdifferent regions of the periphery thereof to working position.

.16. A drill according to claim 10 in which said cutting plate protrudeslaterally beyond the limits of said shank. the protruding regions ofsaid cutting plate being bevelled.

17. In a drill for masonry and rock; a drill shank having a working end,longitudinally extending dust groove means formed in said shank andextending along the shank from said working end, a transverse slotformed in the working end of said shank, a cutting plate formed of hardwear resistant material seated in said slot, a retaining pin extendingthrough said shank substantially perpendicular to the axis of said shankand also engaging said cutting plate and retaining said plate in saidshallow than the groove in said shank.

18. A drill according to claim 17 in which said pin is offset from thecenter of said cutting plate for preload toward the bottom of said slot.

lill

19. A drill according to claim 17 in which said cutting plate has acentral hole, an elastic bushing member in said hole, said pin extendingperpendicular to the plane of said cutting plate and through saidelastic bushing member.

20. A drill according to claim 17 in which said pin is radiallyresilient and has a diameter slightly less than the thickness of saidcutting plate.

21. A drill according to claim 17 in which said cutting plate engagesthe bottom of said slot across the entire diameter of said shank.

22. A drill according to claim 17 in which said slot iscircumferentially spaced from the dust groove means when the drill isviewed axially at the working end, the working end of said dust groovemeans being substantially in the form of a right angle V-shaped notchmeans.

23. A drill according to claim 17 in which said dust groove meanscomprises at least one helical groove formed in the drill shank, saidhelical groove extending to near the working end of the shank, a pair ofdiametrally opposed ax-ial grooves formed in said shank and extendingfrom the working end thereof to and intersecting said helical groove,the plane of said axial grooves being at an angle of about 45 degrees tothe plane of said cutting plate. 7

24. A drill according to claim 17 in which said dust groove meanscomprises a pair of diametrically opposite helical grooves in saidshank.

25. A drill according to claim 17 in which said dust groove meanscomprises at least one helical groove formed in the drill shank, saidhelical groove extending to near the working end of the shank, and anaxial groove formed in the drill shank and extending from the workingend of the shank to and intersects the said helical groove to form acontinuous passage for dust.

26. A drill according to claim 24 in which the helical dust grooveextends toward the working end of the shank beyond the region ofintersection thereof with said axial groove.

27. In a drill for masonry and rock; a drill shank having a working end.longitudinally extending dust groove means formed in said shank andextending along the shank from said working end, a transverse slotformed in the working end of said shank, a cutting plate formed of hardwear resistant material seated in said slot, and a retaining pinextending through said shank substantially perpendicular to the axis ofsaid shank and also engaging said cutting plate and retaining said platein said slot, said pin being moveable in said shank in the axialdirection of said pin to release said cutting plate from said slot, saidcutting plate being symmetrical about at least one central axis which isparallel to the plane of the cutting plate and perpendicular to the axisof the shank when the cutting plate is seated in said slot, each edge ofthe cutting plate facing away from said central axis having a cuttingedge formed thereon. the bottom of said slot being formed forsupportingly engaging the axially inner cutting edge while the axiallyouter cutting edge is in working position, the cutting edges of saidcutting plate being V-shaped and bevelled and the edges of the cuttingplate perpendicular to said central axis being shorter than the otheredges of the cutting plate.

28. In a drill for masonry and rock; a drill shank having a working end,longitudinally extending dust groove means formed in said shank andextending along the shank from said working end, a transverse slotformed in the working end of said shank, a cutting plate formed of hardwear resistant material seated in said slot, and a retaining pinextending through said shank substantially perpendicular to the axis ofsaid shank and also engaging said cutting plate and retaining said platein said slot, said pin being moveable in said shank in the axialdirection of said pin to release said cutting plate from said slot, saidcutting plate when viewed perpendicular to the plane thereof being aregular polygon, all of the edges of said cutting plate being bevelledto form a cutting edge extending about the entire periphery of saidcutting plate, said plate being angularly indexable in said slot forsuccessively presenting different regions of the periphery thereof toworking position, said cutting plate being hexagonal and when seated insaid slot having a pair of edges parallel to the axis of the shank.

29. A drill according to claim 28 in which said pair of edges protrudebeyond the shank at the sides a distance about equal to the height ofthe bevels thereon.

30. In combination with a rock drill having a drill shank which providesa transverse slot at the drill head thereof including a bottom and acutting blade of hard metal installed interchangeably and secured with apin lying approximately at right angles to axis of the drill, the pinengaging in bores of the drill shank and cutting blade which fits inaxial direction of the drill under preload against the bottom, theimprovement therewith which comprises an elastic sleeve arranged betweenthe pin and one of the bores, said elastic sleeve under preload pressingthe cutting blade against the bottom of the slot, said elastic sleevelying symmetrically to the drill axis and at right angles to a plane ofthe cutting blade installed in the transverse slot.

31. A drill in combination according to claim 30. in which said elasticsleeve is installed with preload in the bore of the cutting blade.

32. A drill in combination according to claim 30. in which said elasticsleeve forms a bore for insertion of the pin and said elastic sleeve isinstalled in a bore larger than the borefor the pin.

33. In combination with a rock drill having a drill shank which providesa transverse slot at the drill head thereof including a bottom and acutting blade of hard metal installed interchangeably and secured with apin lying approximately at right angles to axis of the drill, the pinengaging in bores of the drill shank and cutting blade which fits inaxial direction of the drill under preload against the bottom, theimprovement therewith which comprises an elastic sleeve arranged betweenthe pin and one of the bores, said elastic sleeve under preload pressingthe cutting blade against the bottom of the slot, said'elastic sleeveforming a bore for insertion of the pin and said elastic sleeve beinginstalled in a bore larger than the bore for the pin, said elasticsleeve being adhered to an inner surface of the pertaining bore.

34. A drill in combination according to claim 33, in which said elasticsleeve is installed in the bore of the cutting blade.

35. A drill in combination according to claim 34. in which said elasticsleeve is a rubber cylinder.

36. In combination with a rock drill having a drill shank which providesa transverse slot at the drill head thereof including a bottom and acutting blade of hard metal installed interchangeably and secured with apin lying approximately at right angles to axis of the drill. the pinengaging in bores of the drill shank and cutting blade which fits inaxial direction of the drill under preload against the bottom, theimprovement therewith which comprises an elastic sleeve arranged betweenthe pin and one of the bores, said elastic sleeve under preload pressingthe cutting blade against the bottom of the slot, said elastic sleeveforming a bore for insertion of the pin and said elastic sleeve beinginstalled in a bore larger than the bore for the pin, the bore for saidelastic sleeve having an undersized diameter for engagement of the pin.

1. In a drill for masonry and rock; a drill shank having a working end,longitudinally extending dust groove means formed in said shank andextending along the shank from said working end, a transverse slotformed in the working end of said shank, a cutting plate formed of hardwear resistant material seated in said slot, and a retaining pinextending through said shank substantially perpendicular to the axis ofsaid shank and also engaging said cutting plate and retaining said platein said slot, said pin being moveable in said shank in the axialdirection of said pin to release said cutting plate from said slot, saidcutting plate being polygonal when viewed in a direction perpendicularto the plane thereof, at least the axially outer end of the cuttingplate having a point on the axis of the drill shank and incliningrearwardly from the point in both directions when viewed perpendicularto the plane of the cutting plate, the said outer end of the cuttingplate being bevelled on opposite sides to form cutting edges thereon,the working end of said shank being conical and tapering inwardly, therebeing a bottom and side edges of the open end of said slot meeting wherethe slot intersects the conical end of the shank being in about theplanes of the bevels on the outer end of said cutting plate, the angleon the working end of the drill shank being greater than the anglebetween the bevels on the outer end of said cutting plate, said groovemeans in said shank comprising a terminal portion at the working end ofsaid shank disposed immediately forward of the leading side of saidcutting plate at each laterAl end thereof.
 2. A drill according to claim1 in which said pin is generally centrally located with respect to saidcutting plate and is perpendicular to the plane of the cutting plate andextends through said cutting plate.
 3. A drill according to claim 1 inwhich said pin is substantially parallel to the plane of said cuttingplate.
 4. A drill according to claim 1 in which the axis of said pinintersects the axis of said shank.
 5. A drill according to claim 1 inwhich said pin is disposed along said shank between the conical endthereof and the bottom of said slot.
 6. A drill according to claim 1 inwhich said cutting plate is symmetrical about at least one central axiswhich is parallel to the plane of the cutting plate and perpendicular tothe axis of the shank when the cutting plate is seated in said slot,each edge of the cutting plate facing away from said central axis havinga cutting edge formed thereon, the bottom of said slot being formed forsupportingly engaging the axially inner cutting edge while the axiallyouter cutting edge is in working position.
 7. A drill according to claim1 in which said slot is formed with a centering recess therein and saidcutting plate has a protrusion thereon which engages said recess whenthe cutting plate is positioned in said slot.
 8. A drill according toclaim 7 in which the bottom of said slot is perpendicular to the axis ofsaid shank and said centering recess is in the middle of the length ofthe bottom of said slot.
 9. A drill according to claim 7 which includesa hard insert member in said slot and forming the bottom thereof.
 10. Ina drill for masonry and rock; a drill shank having a working end,longitudinally extending dust groove means formed in said shank andextending along the shank from said working end, a transverse slotformed in the working end of said shank, a cutting plate formed of hardwear resistant material seated in said slot, and a retaining pinextending through said shank substantially perpendicular to the axis ofsaid shank and also engaging said cutting plate and retaining said platein said slot, said pin being moveable in said shank in the axialdirection of said pin to release said cutting plate from said slot, thebottom of said slot being in the form of a segment of a cylinder havingan axis disposed outwardly from the working end of the shank andintersecting the axis of the shank at a right angle.
 11. A drillaccording to claim 10 in which said shank has a drilled hole thereininto which said pin closely fits.
 12. A drill according to claim 10 inwhich said shank has a transverse hole therein parallel to the plane ofsaid slot and offset laterally from the axis of said shank, said pinclosely fitting said hole and on one side extending into said slot, saidcutting plate having a groove formed in the side facing said pin toreceive said pin.
 13. A drill according to claim 10 in which a groove isformed along one side of said slot perpendicular to the axis of saidshank, said cutting plate having a groove formed therein on the sidefacing the groove in the shank and in registration therewith, saidgrooves forming a space to receive said pin.
 14. A drill according toclaim 10 in which said cutting plate is polygonal when viewed in adirection perpendicular to the plane thereof, at least the axially outerend of the cutting plate having a point on the axis of the drill shankand inclining rearwardly from the point in both directions when viewedperpendicular to the plane of the cutting plate, the said outer end ofthe cutting plate being bevelled on opposite sides to form cutting edgesthereon, the working end of said shank being conical and taperinginwardly, the side edges of the open end of said slot meeting where theslot intersects the conical end of the shank being in about the planesof the bevels on the outer end of said cutting plate.
 15. A drillaccording to claim 10 in which said cutting plate when viewedperpendicUlar to the plane thereof is a regular polygon, all of theedges of said cutting plate being bevelled to form a cutting edgeextending about the entire periphery of said cutting plate, said platebeing angularly indexable in said slot for successively presentingdifferent regions of the periphery thereof to working position.
 16. Adrill according to claim 10 in which said cutting plate protrudeslaterally beyond the limits of said shank, the protruding regions ofsaid cutting plate being bevelled.
 17. In a drill for masonry and rock;a drill shank having a working end, longitudinally extending dust groovemeans formed in said shank and extending along the shank from saidworking end, a transverse slot formed in the working end of said shank,a cutting plate formed of hard wear resistant material seated in saidslot, a retaining pin extending through said shank substantiallyperpendicular to the axis of said shank and also engaging said cuttingplate and retaining said plate in said slot, said pin being moveable insaid shank in the axial direction of said pin to release said cuttingplate from said slot, and a groove formed along one side of said slotperpendicular to the axis of said shank, said cutting plate having agroove formed therein on the side facing the groove in the shank and inregistration therewith, said grooves forming a space to receive saidpin, the groove in said cutting plate being substantially more shallowthan the groove in said shank.
 18. A drill according to claim 17 inwhich said pin is offset from the center of said cutting plate forpreload toward the bottom of said slot.
 19. A drill according to claim17 in which said cutting plate has a central hole, an elastic bushingmember in said hole, said pin extending perpendicular to the plane ofsaid cutting plate and through said elastic bushing member.
 20. A drillaccording to claim 17 in which said pin is radially resilient and has adiameter slightly less than the thickness of said cutting plate.
 21. Adrill according to claim 17 in which said cutting plate engages thebottom of said slot across the entire diameter of said shank.
 22. Adrill according to claim 17 in which said slot is circumferentiallyspaced from the dust groove means when the drill is viewed axially atthe working end, the working end of said dust groove means beingsubstantially in the form of a right angle V-shaped notch means.
 23. Adrill according to claim 17 in which said dust groove means comprises atleast one helical groove formed in the drill shank, said helical grooveextending to near the working end of the shank, a pair of diametrallyopposed axial grooves formed in said shank and extending from theworking end thereof to and intersecting said helical groove, the planeof said axial grooves being at an angle of about 45 degrees to the planeof said cutting plate.
 24. A drill according to claim 17 in which saiddust groove means comprises a pair of diametrically opposite helicalgrooves in said shank.
 25. A drill according to claim 17 in which saiddust groove means comprises at least one helical groove formed in thedrill shank, said helical groove extending to near the working end ofthe shank, and an axial groove formed in the drill shank and extendingfrom the working end of the shank to and intersects the said helicalgroove to form a continuous passage for dust.
 26. A drill according toclaim 24 in which the helical dust groove extends toward the working endof the shank beyond the region of intersection thereof with said axialgroove.
 27. In a drill for masonry and rock; a drill shank having aworking end, longitudinally extending dust groove means formed in saidshank and extending along the shank from said working end, a transverseslot formed in the working end of said shank, a cutting plate formed ofhard wear resistant material seated in said slot, and a retaining pinextending through said shank substantially perpendicular to the axis ofsaid shank and also engaging said cutting plate and retaining said platein said slot, said pin being moveable in said shank in the axialdirection of said pin to release said cutting plate from said slot, saidcutting plate being symmetrical about at least one central axis which isparallel to the plane of the cutting plate and perpendicular to the axisof the shank when the cutting plate is seated in said slot, each edge ofthe cutting plate facing away from said central axis having a cuttingedge formed thereon, the bottom of said slot being formed forsupportingly engaging the axially inner cutting edge while the axiallyouter cutting edge is in working position, the cutting edges of saidcutting plate being V-shaped and bevelled and the edges of the cuttingplate perpendicular to said central axis being shorter than the otheredges of the cutting plate.
 28. In a drill for masonry and rock; a drillshank having a working end, longitudinally extending dust groove meansformed in said shank and extending along the shank from said workingend, a transverse slot formed in the working end of said shank, acutting plate formed of hard wear resistant material seated in saidslot, and a retaining pin extending through said shank substantiallyperpendicular to the axis of said shank and also engaging said cuttingplate and retaining said plate in said slot, said pin being moveable insaid shank in the axial direction of said pin to release said cuttingplate from said slot, said cutting plate when viewed perpendicular tothe plane thereof being a regular polygon, all of the edges of saidcutting plate being bevelled to form a cutting edge extending about theentire periphery of said cutting plate, said plate being angularlyindexable in said slot for successively presenting different regions ofthe periphery thereof to working position, said cutting plate beinghexagonal and when seated in said slot having a pair of edges parallelto the axis of the shank.
 29. A drill according to claim 28 in whichsaid pair of edges protrude beyond the shank at the sides a distanceabout equal to the height of the bevels thereon.
 30. In combination witha rock drill having a drill shank which provides a transverse slot atthe drill head thereof including a bottom and a cutting blade of hardmetal installed interchangeably and secured with a pin lyingapproximately at right angles to axis of the drill, the pin engaging inbores of the drill shank and cutting blade which fits in axial directionof the drill under preload against the bottom, the improvement therewithwhich comprises an elastic sleeve arranged between the pin and one ofthe bores, said elastic sleeve under preload pressing the cutting bladeagainst the bottom of the slot, said elastic sleeve lying symmetricallyto the drill axis and at right angles to a plane of the cutting bladeinstalled in the transverse slot.
 31. A drill in combination accordingto claim 30, in which said elastic sleeve is installed with preload inthe bore of the cutting blade.
 32. A drill in combination according toclaim 30, in which said elastic sleeve forms a bore for insertion of thepin and said elastic sleeve is installed in a bore larger than the borefor the pin.
 33. In combination with a rock drill having a drill shankwhich provides a transverse slot at the drill head thereof including abottom and a cutting blade of hard metal installed interchangeably andsecured with a pin lying approximately at right angles to axis of thedrill, the pin engaging in bores of the drill shank and cutting bladewhich fits in axial direction of the drill under preload against thebottom, the improvement therewith which comprises an elastic sleevearranged between the pin and one of the bores, said elastic sleeve underpreload pressing the cutting blade against the bottom of the slot, saidelastic sleeve forming a bore for insertion of the pin and said elasticsleeve being installed in a bore larger than the bore for the pin, saidelastic sleeve being adhered tO an inner surface of the pertaining bore.34. A drill in combination according to claim 33, in which said elasticsleeve is installed in the bore of the cutting blade.
 35. A drill incombination according to claim 34, in which said elastic sleeve is arubber cylinder.
 36. In combination with a rock drill having a drillshank which provides a transverse slot at the drill head thereofincluding a bottom and a cutting blade of hard metal installedinterchangeably and secured with a pin lying approximately at rightangles to axis of the drill, the pin engaging in bores of the drillshank and cutting blade which fits in axial direction of the drill underpreload against the bottom, the improvement therewith which comprises anelastic sleeve arranged between the pin and one of the bores, saidelastic sleeve under preload pressing the cutting blade against thebottom of the slot, said elastic sleeve forming a bore for insertion ofthe pin and said elastic sleeve being installed in a bore larger thanthe bore for the pin, the bore for said elastic sleeve having anundersized diameter for engagement of the pin.